Parapellopedon instabilis (Rehn, 1906)

Male calling song
This was a spontaneous song, which could start or finish with brief series of isolated syllables. The main sound was an echeme (fig. 1a, b) lasting 5.3 s ± 2.1 (range: 2,050-9,240; n = 21), and consisting of 34 ± 14 sylla- bles (fig. 1c) (range: 16-72; n = 21) pr oduced at a rate of 6.4 syllables per second (range: 3,9-9,5). The fr equency spectrum (fig. 2a) occupied a broad band, between 2,500 and 12,000 Hz, with a main peak at around 7,000 Hz. The lower quartile (25% of the total energy) was close to 5,000 Hz, the medium quar- tile (50% of the energy) being around 7,500 Hz and the higher quartile (75% of the energy) close to 11,000 Hz. The echeme started as an imperceptible, almost inaudible, sound and increased in intensity after several syllables had been emitted. The sound had a high acoustic intensity. Calls were performed by one male kept in a cage together with other males and females. It always sang alone at some distance (15-25 cm) from the rest of the grasshoppers, undisturbed by them. Sometimes the male sang on the cage floor, sometimes from the top of the cage, or on the vegetation, by synchronously rubbing the two hind femora against the tegminae.

Agreement song
The female’s agreement song also consisted of an echeme (fig. 3a) lasting 8.0 s ± 4.2 (range: 2,400 – 15,196; n = 15), of 32 ± 16 syllables (fig. 3b) as a mean (range: 10- 65; n : 15) pr oduced at a rate of 4.1 syllables per second (max. 6.2; min. 3.4). he frequency spectrum (fig. 2b) occupied a band between 2,000 and 6,000 Hz, with the main peak close to 3,000 Hz. Harmonics of higher frequency reached almost 13,000 Hz. The higher quartile (75%) was close to 11,000 Hz, with the lower (25%) and medium (50%) quartiles being at 3,000-4,000 and 7,000 Hz, respectively. This song seemed more irregular and had a lower acoustic intensity than the male calling song. It was also produced by synchronously rubbing the two hind femora against the tegminae, both hind legs rising rapidly, and descending more slowly, with a swinging movement. Females produced this song in two differ- ent situations, as an answer to the male calling song or spontaneously, with no physical, acoustic or visual inter- action with other individuals.

Disturbance song
Both sexes produced these sounds when the specimens wer e near or in contact with each other. The signals were sometimes emitted in alternation. Male . – This song consisted of a series, differing in length (16.9 ± 11.3 s, range: 5,160-39,000; n = 7), consisting of single and isolated syllables (fig . 4) (27 ± 16; range: 7-47) . The frequency spectrum of this song had the same characteristics as that of the male calling song, a char- acteristic noted by Dumortier (1963) for other species. Each syllable was produced by a sudden rubbing of one hind femur against the tegmina or of both femora acting synchronously. Female . – This song consisted of a series, also differ- ing in length but shorter than that of males (10.3 ± 5.9 s, range: 3,720-17,082; n = 4), composed of 30 ± 10 single and isolated syllables (range: 23-45) (fig. 5). The frequency spectrum of this song had the same characteristics as that of the female song. The sound was produced in the same way as described for males.

Sound producing structures
Along their inner surface, the hind femora of both sexes hav e a stridulator y file that is almost linear , har dly sinu - ate (figs. 6, 7). In both males and females the peg density of the file incr eases to wards the proximal end of the femur , the proximal half of the file has almost twice the pegs as the distal half . In females, the proximal end of the file has more elongated hairs than in males, and the first pegs of the distal end ar e mor e irregularly spr ead than in males. The male file (FL) is shorter than that of the female, but is longer in relation to femur length (FLx100/HFL) than that of the female. Also, it contains mor e pegs than that of the female. The peg density both in the middle zone (PDM) and on the whole file (PD) is greater in males than in females (tab. 3). The male pegs are subconical in shape and have a hardly visible short peduncle. They are inserted in the alveolus, which has a slightly raised margin (fig. 6b, c). The female pegs are more slender than those of males (fig. 7b, c). [1]

References